1. Field of the Invention
The present invention relates to a relay server, a relay communication system and a communication apparatus, which enable a client terminal connected to a remote local area network (LAN) to make communication beyond a wide area network (WAN).
2. Description of the Related Art
Client terminals connected to remote LANs sometimes communicate with one another beyond a WAN. The virtual private network (VPN) can construct a network that appears as if the remote LANs were directly connected to each other. However, it is difficult for the VPN to construct a network having expandability and flexibility.
A relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991 can construct a network that appears as if the remote LANs were directly connected to one another in a similar way to the VPN. Then, unlike the VPN, it is easy for the relay communication system to construct the network having expandability and flexibility.
The relay communication system includes a WAN and a plurality of LANs. Each of the LANs includes a relay server. Each relay server stores relay group information regarding relay servers provided in the relay communication system, and shared resource information regarding resources shared in the relay communication system.
When a client terminal connected to one of the LANs manipulates resources stored by client terminals of other LANs, the relay servers connected to these LANS relay the manipulation for the resources based on the relay group information and the shared resource information.
The number of LANs provided in the relay communication system may sometimes be increased or reduced. The resources shared in the relay communication system may sometimes be updated. However, the relay communication system can update the relay group information and the shared resource information in response to these changes. Then, the relay communication system can construct the network having expandability and flexibility in response to these changes.
Moreover, a relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-140254 can construct a network as if the remote LANs were directly connected to one another in a similar way to Japanese Patent Laid-Open Publication No. 2008-129991. A client terminal determines whether or not it can directly manipulate a shared resource in the relay communication system. In the case where the client terminal cannot directly manipulate the shared resource, it instructs a client terminal, which stores the shared resource, to manipulate the shared resource via a relay server.
In the relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991, the client terminal connected to one of the LANs performs communication with the client terminal connected to another LAN in the following manner.
As a first section, between the client terminal and the relay server that are connected to the one of the LANs, the communication is started. As an intermediate section, between the relay servers connected to the one of the LANs and the another LAN, the communication is relayed. As a final section, between the relay server and the client terminal that are connected to the another LAN, the communication is ended.
In each of the sections, a plurality of call controls may be executed, and a plurality of media sessions may be established. However, specific means for preventing crossover among the plurality of call controls and preventing crossover among the plurality of media sessions in each of the sections is not disclosed in Japanese Patent Laid-Open Publication No. 2008-129991.
In the relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-129991, a change may occur in the number of LANs and client terminals, and in the connection state between the LANs and the client terminals. However, specific means are not disclosed in Japanese Patent Laid-Open Publication No. 2008-129991 for confirming in real time such changes in the number and a connection state of the client terminals and relay servers in the event that they designate destinations for communication.
Moreover, in the relay communication system disclosed in Japanese Patent Laid-Open Publication No. 2008-140254 and Japanese Patent Laid-Open Publication No. 2008-129991, each of the client terminals sometimes downloads a shared resource in order to edit the shared resource that cannot be directly manipulated thereby. An entity of the downloaded resource and an entity of such an original shared resource are present separately from each other, and accordingly, it is possible to edit the respective resources separately from each other. However, in the case where the respective resources are edited separately from each other, it has not been possible to unify and manage information recorded in the respective resources.